Proteolytic degradation of heme-modified hepatic cytochromes P450: A role for phosphorylation, ubiquitination, and the 26S proteasome?
Proteolytic degradation of heme-modified hepatic cytochromes P450: A role for phosphorylation, ubiquitination, and the 26S proteasome?
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DOI：
10.1006/abbi.1999.1138
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发表时间：
1999-05-01
影响因子：
3.9
通讯作者：
Correia, MA
中科院分区：
文献类型：
--
作者：
Korsmeyer, KK;Davoll, S;Correia, MA
肝内质网（ER）蛋白质，细胞色素P450（P450），在体内以广泛变化的半衰期翻转。我们和其他人（Correia等，，Arch. Biochem. Biophys. 297，228，1992;和Tierney等人，《生物化学与生物物理学基础》293，9，1992）先前已经表明，在完整动物中，3A和2 E1亚家族的肝P450首先被泛素化，然后在其药物诱导的自杀失活后被蛋白水解。我们对完整大鼠肝细胞和含有天然P450和通过蛋白质的血红素修饰失活的P450的ER制备物的发现揭示了血红素修饰的P450的蛋白水解降解需要胞质ATP依赖性蛋白水解系统而不是溶酶体或ER蛋白酶（Correia等人，《生物化学与生物物理学基础》297，228，1992）。使用纯化的枯烯过氧化氢灭活的P450（大鼠肝P450 2B 1或3A和/或重组人肝P450 3A 4）作为模型，我们现在证明这些血红素修饰的酶确实被泛素化，然后被26 S蛋白酶体蛋白水解，但不被其20 S蛋白水解核心蛋白水解。我们的研究表明，这些血红素修饰的P450的泛素化是在它们的磷酸化之前进行的。与其他几种细胞蛋白质一样，这种P450磷酸化是否确实是它们降解所必需的还有待确定。尽管如此，这些发现表明，膜锚定P450被包括在不断增长的类ER蛋白，经历泛素依赖性26 S蛋白酶体降解。(C)北京：科学出版社.
The resident integral hepatic endoplasmic reticulum (ER) proteins, cytochromes P450 (P450s), turn over in vivo with widely varying half-lives. We and others (Correia ct al,, Arch. Biochem. Biophys. 297, 228, 1992; and Tierney ct al., Arch. Biochem. Biophys. 293, 9, 1992) have previously shown that in intact animals, the hepatic P450s of the 3A and 2E1 subfamilies are first ubiquitinated and then proteolyzed after their drug-induced suicide inactivation. Our findings with intact rat hepatocytes and ER preparations containing native P450s and P450s inactivated via heme modification of the protein have revealed that the proteolytic degradation of heme-modified P450s requires a cytosolic ATP-dependent proteolytic system rather than lysosomal or ER proteases (Correia ct al., Arch. Biochem. Biophys. 297, 228, 1992). Using purified cumene hydroperoxide-inactivated P450s (rat Liver P450s 2B1 or 3A and/or a recombinant human liver P450 3A4) as models, we now document that these heme-modified enzymes are indeed ubiquitinated and then proteolyzed by the 26S proteasome, but not by its 20S proteolytic core, In addition, our studies indicate that the ubiquitination of these heme-modified P450s is preceded by their phosphorylation, It remains to be determined whether, in common with several other cellular proteins, such P450 phosphorylation is indeed required for their degradation. Nevertheless, these findings suggest that the membrane-anchored P450s are to be included in the growing class of ER proteins that undergo ubiquitin-dependent 26S proteasomal degradation. (C) 1999 Academic Press.